Basement membranes (BMs) are necessary for lung development and restoration of normal alveolar architecture when the lung has sustained damage. However, little is known about alveolar BMs in the context of alveolar damage and repair. Laminins are integral BM glycoproteins. Laminin-5 (Ln-5), comprised of laminin chains alpha3, beta3, and gamma2 affects epithelial cell structure and function generally, and is present in alveolar BMs, but its roles specifically in lung development and alveolar damage are unknown. In Aim I we will study the role of Ln-5 in lung development and alveolar damage using mice deficient in Ln-5 as a result of targeting the laminin gamma2 gene. However, mice with a global knockout of the laminin gamma2 gene die <5 days after birth with mucosal and cutaneous sloughing. Because of this we will generate lung-specific, inducible laminin gamma 2-deficient mice. These mice will be used to examine the effect of Ln-5 deficiency on the later stages of lung development and the response to various models of alveolar damage, including Pseudomonas aeruginosa-induced alveolitis, bleomycin-induced pulmonary fibrosis, and cigarette smoke-induced emphysema. Their lungs will be evaluated for structure, expression of extracellular matrix genes and inflammatory cell recruitment. In Aim II we will assess the effects of Ln-5 on alveolar type epithelial cell (AEC) migration. These studies will involve AECs isolated from wild type mice and mice with the lung- specific, inducible knockout of laminin 72. In Aim III, using in vivo and in vitro models like those described in Aims I and II, we will study mice with deficiencies of matrix metalloproteinases (MMPs) -2 or -14 to determine the roles of these MMPs on responses to alveolar injury and AEC cell migration. MMPs -2 and -14 are of particular interest because they are known to affect epithelial cell migration via effects upon Ln-5, but their role in AEC functions has not been determined. Because neutrophils are often prominent in alveolar injury we will also explore the effects of neutrophil proteinases upon Ln-5 and its effects on AEC cell functions. The studies proposed in this grant application will contribute new information about alveolar BMs, an important structure in serious, common lung disorders, including the acute respiratory distress syndrome, pulmonary fibrosis, and emphysema.